diff --git a/Aoc.lean b/Aoc.lean
deleted file mode 100644
index f7027a9..0000000
--- a/Aoc.lean
+++ /dev/null
@@ -1,3 +0,0 @@
--- This module serves as the root of the `Aoc` library.
--- Import modules here that should be built as part of the library.
-import Aoc.Basic
\ No newline at end of file
diff --git a/Aoc/1/Basic.lean b/Aoc/1/Basic.lean
deleted file mode 100644
index bec6648..0000000
--- a/Aoc/1/Basic.lean
+++ /dev/null
@@ -1,30 +0,0 @@
-def rawFile := IO.FS.readFile "Aoc/1/input.txt"
-
-def parseRaw (rawFile: IO String): IO (List (Int × Int)) := do
-  let raw ← rawFile
-  let splitted := raw.splitOn "\n"
-  let listOfTwoElementList := List.map (λ x => x.splitOn "   ") splitted
-  let dropped := List.dropLast listOfTwoElementList
-  let pairs := List.map (λ x => ((List.get! x 0).toInt!, (List.get! x 1).toInt!)) dropped
-  pure pairs
-
-set_option maxRecDepth 10000
-#eval parseRaw rawFile
-
-def input: List (Int × Int) := [(3, 4), (4, 3), (2, 5), (1, 3), (3, 9), (3, 3)]
-
-def transpose (input: List (Int × Int)) := input.foldl (fun (acc1, acc2) (x, y) => (acc1.append [x], acc2.append [y]) ) ([], [])
-
-def solve (input) := transpose input
-      |> (λ (a, b) => (List.mergeSort a, List.mergeSort b))
-      |> (λ (a, b) => a.zip b)
-      |> (λ l => l.map (λ (x, y) => (x - y).natAbs))
-      |> List.foldl Nat.add 0
-
-def solveIO (inputIO: IO (List (Int × Int))) : IO Nat := do
-  let input ← inputIO
-  pure $ solve input
-
-#eval solveIO $ pure [(3, 4), (4, 3), (2, 5), (1, 3), (3, 9), (3, 3)]
-
-#eval solveIO $ parseRaw rawFile
diff --git a/Aoc/Day1/Solution.lean b/Aoc/Day1/Solution.lean
new file mode 100644
index 0000000..f3d4edf
--- /dev/null
+++ b/Aoc/Day1/Solution.lean
@@ -0,0 +1,33 @@
+instance : Monad List where
+  pure := List.singleton
+  bind := List.flatMap
+
+def List.sequence {m α} [Monad m] (lst: List (m α)) : m (List α) := List.mapM id lst
+
+def parse (raw : String) : Option (List (Int × Int)) :=
+  raw.splitOn "\n"
+    |> List.map (String.splitOn · "   ")
+    |> List.map (List.map String.toInt?)
+    |> List.map List.sequence
+    |> List.filter Option.isSome
+    |> List.sequence
+    |> Option.map (List.map (λ x => match x with | [a, b] => some (a, b) | _ => none))
+    |> Option.map List.sequence
+    |> Option.join
+
+def solve (input: List (Int × Int)) : Nat :=
+  input.unzip
+    |> λ (a, b) => List.map (λ (x, y) => (x - y).natAbs) (a.mergeSort.zip b.mergeSort)
+    |> List.sum
+
+def fakeRawInput: String := "3   4\n4   3\n2   5\n1   3\n3   9\n3   3"
+#eval solve <$> parse fakeRawInput
+
+def fakeParsedInput: List (Int × Int) := [(3, 4), (4, 3), (2, 5), (1, 3), (3, 9), (3, 3)]
+#eval solve fakeParsedInput
+
+def parseAndSolve : String → Option Nat :=
+   Option.map solve ∘ parse
+
+def rawInput := IO.FS.readFile "Aoc/Day1/input.txt"
+#eval parseAndSolve <$> rawInput
diff --git a/Aoc/1/input.txt b/Aoc/Day1/input.txt
similarity index 100%
rename from Aoc/1/input.txt
rename to Aoc/Day1/input.txt
diff --git a/Main.lean b/Main.lean
deleted file mode 100644
index 73eb7c6..0000000
--- a/Main.lean
+++ /dev/null
@@ -1,4 +0,0 @@
-import Aoc
-
-def main : IO Unit :=
-  IO.println s!"Hello, {hello}!"